Where does the standard XJ12 fit in though? Was this offered alongside the Sovereign H.E./V12 etc, or was it merged with the Sovereign line in '84 when the Sovereign was changed from Daimler to Jaguar? And what do the chrome strips mean? 1990+ V12?

Interesting stuff. We get so close to something useful and then it begins to crumble at the edges. As for plaque badges (but not V12 related) /vehicle_482308-Jaguar-XJ6-Series-III-1986.html is interesting - registered 01-01-86 so days before my suggested start of plaque badges, it has non-plaque (hoorah!). So best guess at the moment could be that V12 (under whatever name) got plaque in late 85 a few months before lesser models OR V12 and Sovereigns got plaque in late 85 a few months before normal XJ6. But plaque seems safe for everything made after Jan 86, and probably for everything we'd call 86my onwards.

Chrome strips confusing until a penny dropped. In UK terms they mean Daimler VdP (both 6 and 12 versions offered) but for all the German examples, Daimler was probably excluded for naming reasons, so my guess is German Daimlers renamed Jaguar VdP as US system (so a Daimler VdP becomes Jaguar VdP VDP??). So we have quite a few German Jag grilles with chrome strips, but they don't have to be 90+ V12 only - just mid 80s+ Daimler VdP 6 and 12 equivalents. Any local info useful.

Yes, but it was a plate suffix change point for the start of the next year, so everyone liked to have the newest plate. Cars were sold in Dec with the new registration and registered and taxed from Jan 1 - so people could not legally use them until Jan 1. Garages would open on Jan 1 for people to collect their shiny new delights, and then they'd drive round showing off to their neighbours. These things mattered in English suburbia, and there is still a slight resale advantage for a January registration over the preceding Nov/Dec, despite the plate change months now being March and September.